In recent years, with the aim of reducing a cost and improving flexibility of a system, cloud computing has been widely used. As a technology for building a cloud computing platform thereof, Infrastructure as a Service (IaaS) has been proposed. IaaS is a technology that provides infrastructure, such as equipment, networks, or the like including virtual servers needed to operate external information systems, such as network environments, as services on the Internet.
IaaS provides information infrastructure to users via the Internet. Furthermore, in IaaS, network resources are often supplied to a plurality of users. Because of this, in data centers that implement IaaS or the like, the communication quality needs to be improved. Specifically, in IaaS, the high communication performance, such as a high band width or a low latency, and fairly sharing network resources, such as fair band allocation and low jitter, i.e., a reduction in fluctuations in latency, are needed.
In order to respond to these demands, to improve the communication quality, control of allocating current virtual machines (VM) and band control in virtual switches are performed. However, on calculation, even if VMs are appropriately disposed, there may be a case in which congestion or the like occurs depending on the actual operational state. Consequently, due to exhaustion of buffer resources or capacity limit of the switching performance, a decrease in the communication performance and an unfair share state of the network resources may possibly occur. In order to cope with such states, it is conceivable to dispose VMs by allowing each of the VMs to have, for example, a sufficient band; however, the use efficiency of the resources is decreased and thus a cost may possibly be increased.
Thus, it is preferable to perform, when, for example, congestion occurs, scheduling in accordance with the policy that is used to implement a fair state. The fair mentioned here indicates that all of the flows are fairly treated. The flow mentioned here indicates a series of packets that are classified by a condition that includes the addresses of the transmission source and the transmission destination, a port number, or a protocol number.
Thus, conventionally, a technology of switching paths in order to avoid congestion has been proposed. Furthermore, a technology that controls, by using a plurality of transmission queues, bands in accordance with the scheduling of the transmission queues has been proposed.
Patent Document 1: U.S. Pat. No. 8,867,560
However, if the path are switched at the midpoint of the flow, the reception order of packets may possibly be changed. Furthermore, in the technology that controls the bands in accordance with the scheduling of the plurality of transmission queues, there is a problem as follows. For example, it is difficult to allocate dedicated queues to all of the flows because the number of queues is limited. In addition, it is difficult to perform the band control for each flow because the allocation of the scheduling or the queues is fixed. Furthermore, when performing the scheduling using a Weighted Round Robin (WRR) technique or a Deficit Round Robin (DRR) technique, packets are often continuously sent from a single queue. Consequently, a load tends to be applied on the reception side of packets and thus the communication performance may possible be decreased.